The present invention relates to a rotary drum filter and particularly to a method and apparatus of securing or fastening a filter cloth to the drum of a rotary vacuum filter.
In one type of conventional rotary drum filter presently in use, the drum has a plurality of axial dovetail slots spaced at predetermined intervals around the drum. The filter cloth is placed around the drum and is wedged or forced into the dovetail slots by means of a caulking cord. During a blowback cycle, the caulking cords tend to roll out of their respective slots thereby freeing the filter cloth and thus rendering proper filtering impossible. For moderate to severe blowback pressures, it has been necessary to employ wires or bands to hold the filter cloth in place around the drum. Such wires or bands have a number of disadvantages. They restrict the flexing of the filter cloth, thereby reducing the effectiveness of the discharge. They reduce the filter area by as much as ten percent. They cause channeling during the wash cycle. Finally, they limit the removal of the filter cake with a "doctor" knife.
The present invention provides an apparatus and method which completely eliminates the need for wires and bands.
An object of the invention is to provide a deformable metal means which firmly fastens or secures a filter cloth in an axial slot on a rotary drum. Such metal means not only provides torsional stability, preventing rolling from the slot, but also holds the filter cloth sufficiently securely in place that the cloth itself will tear before it can be pulled from the slot.
A primary object of the present invention is to provide a flexible or deformable metal screen which can be secured over a portion of a filter cloth in a slot and wedged therein by means of a caulking cord.
Another object of the present invention is to provide a multiple stranded metal wire cable which can be wedged or forced into a dovetail slot of a rotary drum for firmly securing or holding a portion of a filter cloth in place on the drum. The cable is sufficiently flexible to deform into the slot, but offers sufficient torsional resistance to inhibit rolling of the cable from the slot.
Other objects and advantages of the present invention will become more readily apparent from a consideration of the following descriptions and drawings.